A phase shifter is an apparatus capable of adjusting a phase of a wave, and is a core part of a base station antenna. The phase shifter changes a beam scanning angle of an array antenna to flexibly adjust a coverage area, that is an antenna pattern, of an antenna beam. Performance of the phase shifter directly affects a pattern, a gain, a dimension, even manufacturing costs, and the like of the base station antenna. Therefore, design and improvement of the phase shifter are important in overall design of the base station antenna.
To manufacture cost-effective phase shifters with high phase adjustment precision, in the prior art, a Chinese patent (Application No. 200520121325.1) in 2007 discloses a phase shifter with a continuously variable phase. Referring to FIG. 1, one end of a fixed transmission line 411 and one end of a fixed transmission line 413 are each provided with a lengthwise slot, directions of the slots face towards a “ground” layer, and the “ground” layer is a metal cavity 400. Two arms of a movable transmission line 412 are respectively disposed in the slot of the fixed transmission line 411 and the slot of the fixed transmission line 413. A total length of a transmission line formed by the fixed transmission line 411, the fixed transmission line 413, and the movable transmission line 412 is changed by using a mechanical transmission device (not shown in the figure), thereby continuously changing a phase between a coaxial connector 401 and a coaxial connector 402. However, to ensure coupling connection between the fixed transmission line and the movable transmission line, the mechanical transmission device further needs to apply, in a direction towards the slot, pressure on the movable transmission line. The phase shifter is complex for operation, and has a high performance requirement for the mechanical transmission device.
A second Chinese patent (Application No. 200520065549.5) discloses a phase shifter. Referring to FIG. 2, a structure of a phase shifter shown in FIG. 2 is similar to a structure of the phase shifter shown in FIG. 1. A difference lies in that structures of a fixed transmission line 3 and a movable transmission line 6 that are shown in FIG. 2 are tubular structures. During the assembly, the fixed transmission line and the movable transmission line need to be aligned with each other, or otherwise, an isolating layer between the fixed transmission line and the movable transmission line can be damaged, which causes severe interference to a communications system.
In addition, a specific distribution manner of a circuit on the movable transmission line is not mentioned in the foregoing two patents.